(i) Technical Field
The present invention relates to a recording medium and an infrared reading method.
(ii) Related Art
A recording medium which records information by an arrangement of plural marks which are formed with an infrared absorbing toner that absorbs infrared rays is known. Examples of the information recorded on the recording medium include identification information for identifying a recording sheet and position information that represents coordinate positions on a recording sheet. As an example of a device that reads the identification information or the position information from the recording medium, a pen-shaped handheld reading device which includes an LED (Light Emitting Diode) that emits infrared rays and a CCD (Charge Coupled Device) image sensor that detects infrared rays is known.
However, when marks formed on the recording medium using the pen-shaped device described above are read, the reading angle generally changes with respect to the surface that is to be scanned. Thus, when the reading direction of the device is identical to or approaches the direction where the intensity of light reflected from the surface of the recording medium increases, the intensity of the infrared ray reflected from a mark and received by the device is equal to or more than a threshold value determined for the device. As a result, the mark is erroneously recognized as not being present.